Electric compensator



G.'W. PIERCE I ELECTRIC cbmmnsnoa Filed June 25, 1919 5 sheets-sheet 1 Aug. 28,

G. W. PIERCE ELECTRIC COMPENSATOR Fled June 25, 1919 3 :iq e W IN VEN TOR.

G. w. PIERCE ELECTRIC COMPENSATOR Aug. 28, 1928.

s Sheets-Sheet Filed June 25, 1919 INVENTOR.

Aug. 28, 1928. G. W. PIERCE ELECTRIC COMPENSATOR FiledJune 25, 1919 5 Sheets-Sheet 4- fi e M7201,

IN V EN TOR.

Aug. 28, 1928. 1,682,712

G. w. PIERCE ELECTRIC COMPENSATOR Filed June 25, 1919 5 Sheets-Sheet 5 2%0543, hfg uw IN V EN T OR.

Patented Aug. 28, 1928.

UNHTE TES GEORGE SIGNAL COMPANY, OF

w. rrnncn, or cmnnmen, massacnusnrrs, ASSIGNOR- 'ro sn roa'rmnn, mama, A conrorwrron' or MAINE.

ELECTRIC COM'PENSATOR.

Application flled-June 25,

,The present invention relates to compensation, and more particularly to electr c comvp'ensators. An electric compensator is a device for introducing suitable time retardation into one or more electrical currents, in such a way that electrical disturbances set up in two or more receiving elements may be brought into combination in a useful manner. The electric compensator may be employed to determine the direction of distant sources of radiant energy, particularly sound sources. Some of the principles employed are adaptable to the determination of the direction of sources of electric waves.

energy sources, the compensator is adaptable also to use in focusing the receiving system on one ofseveral radiant energy sources and thus eliminating or suppressing energy from undesired sources.

In the drawings Fig. 1 is a diagrammatical view illustrating the principle of the electric compensator as applied to two receiving units.

Fig. 2 is a diagrammatic development showing the principle of operation of the electric compensator switch, n connection with its circuits, for tworeceiving units.

Fig. 3 is a diagrammatic bottom lan view of the. switchandconnections use for two receiving units.

Fig. 4 is a cross section showing the structure of the rotary switch which is shown diagrammatically in Fig. 3.

Fig. 5 is a wiring diagram of the electric compensator and its connections for two lines of twelve receiving units each, with a development of the switch. Fig. 6 is a diagram showing in perspective the switch disc and electrical connections for a compensator for two lines of twelve receiving units each. j

For purpose's'of illustrating the principle of operation let us suppose that there art two receiving elements actuated by; wave energy, such as sound waves, coming from some particular'direction. general this energy will I strike-one of the receiving elements before it strikes the other receiving element. If currents are setup in two-receiving elements, the

current in one element will be in advance of By mtIO .the'cnrrent in the other element. ducing into the advance element, suitable means for retarding the current'in it, it is In addition to the 15 determination of the direction of radiant 1919. Serial No. 306,689i.

possible to bring the currents in the two elements into phase. These two currents in phase may now be introduced into a translat-' ing device which will give a greater response than would be obtained if the two currents were out of phase. The amount by which the currents in the original receiving elements were out of phase will depend upon the direction of the source of wave energy with respect to a line through the two receiving elements, so that the amount of retardation that is introduced to bring them into phase can be used to determine the angle between the direction of wave source and a line oftlie receivers.

)Nith theuse of two receiving elements two separate translating devices may be used, particularly if the translating devices are employed with auditional interpretation, for example in the case of the use of telephone receivers as translating devices. With two telephone receivers as translating devices one may be applied to each ear. With such an arrangement if one of the telephone receivers be stimulated in advance of the other the I sound will appear to come from the side on which is the advance receiver. By introducing retardation into the line communicating with the advance receiver the sound produced by it may be retarded by such an amount that it will be in phase with the sound at the other can Under these conditions the sound will be physiologically located in a median plane through the head of the observer, or is said to be inaurally centered. The physiological perception of binaural centering is found by v experience to'be accurate and refined. The direction of a source of energy, particularly a source of sound, can be determined with greater definiteness and discrimination by the use of a large number of receivin devices in proper geometric arrangemen A simple and eflicient arrangement consists in placing the several receivers equall spaced in a straight line. Sound coming in any. particular direction will strike these several receivers in succession so that the impulses in each receiver will have a fixed time interval behind the impulses in the adjoining receiver nearer to the source of sound. The amount of this time interval will depend upon the angle between the common base line of the receivers and the linealong which the. sound is traveling. The determination of this lating device and thereby get a maximum response. As an alternativemethod, what may be called the forward half of the receiving line has its receiving elements severally connected through electric circuits to a translating device, such as a telephone receiver, applied to one ear, while the other half, which may be called the rear half of the receiving line, has its receiving elements connected through electric circuits to a translating'device, such as a telephone receiver,

applied to the other car. 'By adjusting the time retardations of the transmitting circuits the receiver at each ear may be made to have maximum response, and the responses of the two receivers may at the same time be brought into such a phase relation that the sound will 1 1n apparatus for the direction detection of I other forms of radiant or wave energy, such be binaurally centered. This latter combination determines direction by a reading of acalibration corresponding to the adjustmentsofv the retardin elements; said adjustment being characterized by simultaneous maximum and binaural centering. The operation in this case is equivalent to focusing the line upon the source of sound and results in an elimination or suppression of disturbing sounds from sourceshaving diflerent angular bearings.

In the drawings the invention is illustrated as embodied in apparatus for determining the direction of sound waves and more particularl for determining the direction of submarine sounds. It is to be understood, however, that the invention it not limited to this type of apparatus but may be embodied for example as electric waves. a

Referrlng to the illustrated embodiment 'of the invention and particularly to Fig. 1,

two receivers of the microphone type are indicated by reference numerals 1 and 2. These receivers are spaced apart a redetermined distances" For submarine sound detection receivers.'are spaced apart usually about five or six feet. supplied by a common batte phone 1 is connected throug of a transformer 5, and the 3. The microthe primary 4, microphone 2 is v connected through the primary fi, of a similar transformer 7.

e secondary 8, of the transformer 5, is connected through a retardation line consisting of inductance elements 9,10 and 11 in series, andcapacit'y elements The microphones 1 and 2 areand 22 inshunt, to the right hand receiver 23,

of the telephone head piece. For convenience an inductance such as 9, with its adjacent condenser 12, may be designated a section of the line. Instead of connecting the condenser of a section to the terminal of the inductance of the same section, it may be connected to the center of said inductance, as illustrated in Fig. 2.

The several sections are computed to each introduce a certain time lag into the current tray ersing them from the transformer secondary to the translating device, and the time lag introduced into the line by one of the sections may be designated as t. In practice in submarine receptlon of sound it has been found convenient to make t equal to about .000065 seconds. This is approximately the time required for sound to travel four inches in water..

Let the microphone receivers 1 and 2, be four feet apart. Suppose a sound strikes the receivers coming from a direction at right angles to the base line joining them. The two receivers will be excited simultaneously and if the lines to the respective translating ear pieces 15 and 23, have sections, the sound will be binaurally centered. Suppose, however, that the sound is traveling in a line in the direction of the base llnejoining the microphones and strikes the receiver 1, first. It will strike the receiver 2, later b the time required for the sound to travel our feet in water. If two lines to the head piece have the same number of retarding sections in them, the sound will be binaurally located in the receiver 15, which we have supposed applied to the left ear. However, if an excess of twelve retarding sections, each equivalent to four inches in water.- are interposed in the line between the transformer 5, and the ear piece 15, the sounds in the two ear pieces will occur simultaneously and the sound will be binaurally centered. For any direction intermediate between the end-on direction and the perpendicular direction the time required to travel from the first receiver to the second will be intermediate between the time to travel four feet in water and zero time, so

that a numberof sections intermediate bethe same number of the conducting disc 85, as shown in Fig. 4, capable of rotation and provided on its upper face with a calibrated angular scale which may be read through the window 86. The slip rings, 82 and 83, are carried on the stationary bottom plate 87, of insulating material in position to have sliding contact with the brushes, 80 and 81, which are carried by the rotatable disc 85, and are connected with the blocks, 65 and 66, respectively.

As shown in Fig. 3, the retardation line of the compensator is divided into twenty-three sections numbered 90 to 112, respectively. Each section includes an inductance 42, and a capacity 43. The capacities 43, are connected in multiple to a common connection 113, going to line 114, which joins the middle point between the receivers 33 and 34, to one side of the transformers 35 and 36. The ends of the inductance of 42, are connected to the inner and outer brushes 120 and 121, of adjacent pairs of brushes. As shown in Figs. 3 and 4, the inner and outer brushes 120 and 121, are arranged in pairs arranged in two c0ncen tric circles under the series of rotating blocks. For convenience these pairs of brushes are designated by reference numbers 130 to 153 inclusive. As shown in Fig. 4, the series of pairs of brushes 1-20 and 121, are carried upon insulating mountings on the stationary bottom plate 87.

If the rotatable series of blocks has the position shown in Fig. 3, the current from the I secondary of the transformer 35 goes through 5 the lead line 160 to the outer brush 121 of the pair of brushes numbered 130, then across block in contact with this pair to the inner brush 120 and to the inductance 42 of section 90, then across the pair of brushes 131 through the inductance 42, of section 91, and so on through sections 92 to 100 inclusive to the outer brush 121 of the air of brushes numbered 141. This brush ears against the L-shaped block 65. The current passes through the block to the brush and slip ring 82 to the ear piece 33 of thetelephone receiver and through the connection 114 back to the transformer secondary. Similarly the current from the secondar of the transformer 36 goes through the lead 161 to the outer brush 121 of' the pair of brushes numbered 153, across the conducting block to the inner brush 120 of this pair, then through the inductance 42 of the section of the line numbered 112 and so on through the sections of the line 111 to 102 inclusive, to the inner brush. 120 of the pair of brushes numbered 142. This brush bears on the L-shaped block 66. The current passes through the block 66 and its brush 81 to the slip ring 83, to the ear piece 34 of the telephone receiver set, and through the common connection 114 to the transformer secondary.

In this position of the parts there are eleven sections of the retarding line of the compentransformer andthe compensator will bin-.-

aurally center a sound commg at right angles.

to the base line joining the microphone receivers 31 and 32. If'the sound comes at an oblique angle and reaches the receiver 31 first, the handle 165 of the compensator is turned to rotate the plate 85 with its series of conducting blocks and introduce more sections in series with the secondary of the transformer 35 and the head piece receiver 33, and subtract sections from the portion of the line in series with the secondary of the transformer 36 and receiver 34. The handle is turned until the sound is binaurally centered in the ears of the observer. When so set the excess of compensator sections in series with the secondary of the transformer 35, retards the. current so that the sound in the two receivers is in phase. The base line between the microphonic receivers 31 and 32 is known. The time retardation caused by eachsection of the compensator line is known, bein calculated from its electric constants and t e angular scale 85 is calibrated in degrees from such computation. The observer can determine the angle of incidence between the sound and the base line of the microphonic receivers 31 and 32 by reading the scale.

The computation of the proper constants of the retardation line used in the electric ccf mpensator is as follows:

R=resistance per section of the line C=capacity per section of the line L=inductance per section of the line the current after traversing. n sections of I =the input current, I the current traversing the nth section of the line. The quanlow the line will have the value I =I e-. Where tity a in the exponent is called the attenuation constant per section of the line.

i The current after traversing n unitsof the line will lag behind the input current by an amount M, where t is the time retardation er section of the line. see page 294, Electric oscillations and electric waves, by applicant, published 1920 by McGraw-Hill Book Co., tion of further equations set forth in this specification see Chapter XVI of said book, especially pages294, 296 (Sec. 264) 305, 314, 315.

If {LC be s'ufiiciently small in comparison with the period of all significant audible frequencies, a a mathematical investigation shows that g and for the deriva- (For a similar equation source of the sound from the baseline joining the receiving microphones. When the direction of the sound is determined by introducing variable amounts of time lag into the circuits from the microphones to the tele phone head piece, the process is known as variable compensation. This permits the microphones to be fixed in position. The 'direction may, however, be determined by what is known as fixed compensation. If, for example, the microphones 1 and 2. are connected to the respective ears through electric lines having the same time retardation, then the sound may be binaurally centered by revolving the microphone system until the sound is binaurally centered at which point the sound will be at right angles to the base line adjoining themicrophones. Or, the circuit to one microphone may be given a time retardation equal to the time to travel from one microphone to the other, in a direct line. In this casethe sound may be binaurally centered by revolving the line of the microphones until it points toward the sound, the microphone having the excess time lag introduced into its connections, being nearest the sound. I

Returning to the matter of variable com pensation, Fig. 2 is a development of the switch mechanism for varying the compensation byintroducing excess of compensating elementsinto the telephone receiver responsive to the one or the other of the microphone receivers.

Referring to Fig. 2, referen e numerals 31 and 32 indicate two micropl sones suitably spaced apart, and-33 and 34 the two receivers of atelephone head piece respectively responsive to microphones 31 and 32. 35 and 36 are two transformers, called input transformers, by means of which electromotive forces produced by the periodic microphone currents are impressed upon the two ends of the comnsator. The compensator is illustrated as avin five elements, numbered from 37 to 41 inc usive, each element comprising an inductance 42, and capacity, 43. A number of stationary brushes are arranged in pairs and indicated by reference numerals 44 to inblocks,

elusive. A series of movable conducting 56 to inclusive, is arranged to be moved alon under and bridge the stationary brushes. T e end blocks, 56 to 64 and 67-to 75 inclusive, bridge across between the twobrushes of a pair. The blocks, 65 and 66, are L-shaped as shown in the drawin and are respectively connected to the telep onehead piece receivers, 33 and 34. These L-shapl d blocks divide the system of circuits in sue 'a way that the current from the transformer 35, goes through the telephone receiver 33, and the current from 'the transformer 36, goes though the telephone receiver 34, independently, since the connection 7 6, from the common point of the are all alike and are arranged to.

two telephone receivers to the common point of the two transformer secondaries has negligible resistance. In the position shown in the figure the current through the secondary of the transformer 35, and the telephone receiver 33, goes through two sections, 37 and 38, of the compensator line, the section 39, having its inductance short circuited by the block 65, while the current from the transformer 36 to the, telephonereceiver 34, oes through one section of the compensator ine, the section 40, having its inductance short circuited by the block 66. It now the system of blocks is moved to the left by an amount equal to the distance between the centers of two adjacent blocks, the short circuit on the coil of section 40, is opened so that the current on this side now passes through two sections, 40 and 41, of the compensator. This movement does not change the number of sections of the compensator in series with receiver 33. By examination, it is seen that a movement to the left of the system ofblocks b another step equal to the distance between t 1e centers of the two adjacent blocks will short circuit the inductance of section 38, leaving only one section of the line in series with telephone receiver 33; while the efiect of this motion does not change-the number-of sections in series with telephone receiver 34. This operation carried on successively results in changes amounting to an increase of the excess of elements to one of the telephone'receivers by an amount equal to one section for each step in the translation of the blocks. It is to be noticed that this operation nowhere results in an interruption or significant variation of the amplitude of the current to the two telephone receivers.

By this step-by-ste movement to the blocks all of the sections o the line may be put in I serieswith the telephone receiver 33, or with the telephone. receiver with one telephone receiver and part in series with the other.

In practice the number of sections in the compensator line is usuall greater than that shown schematically in F 1g. 2, and the movable blocks aremo'unted, insulated from one another, upon a rotating disc. The switch, as constructed for twomicrophones, is shown diagrammatically in Fig. 3. Reference numera'ls 33 and 34 indicate the two receivers 01 a telephone head piece, sive to microphones 31 and 32, bein connected through the transformers 35 an 36, in the same way as shown in Fig. 2. The blocks, 65

34, or part in series.

You

respectively responand 66, are connected respectively to the telehone receivers,

rushes, 80 and 81, and the slip rings, 82 and 83, respectivel These correspond to blocks 65 and 66 of 67 to 75 inclusive, correspond to similarly numbered blocks onFig. 2, 7

' The blocks are mounted on an insulating 33 and- 34, through the I ig. 2. The blocks 56 to 64 and tain asagna device shall satisfy approximately the equation Another relation is that the attenuation a, of a section of the line is 3) Fgyg.

supposed that it is desired to make the time retardation per section of the line have the value t= 6.5 X 10' seconds; then (4) /L( =6.5X' seconds "by equation (1).

Suppose that the translating device has an impedance of say 260 ohms. Then by. equation (2) we have (5) .\/%=260 ohms. Taking the product of (5) and (4) we ob- L=.O169 henry. Taking the quotient of (4) and (5) we obtain 7 C=.25 X 10. farads= .25 microfarads.

The values given in equations (6) and (7 are the required values of inductance and capacity for an electric compensator for the given conditions.

' Let us next investigate theattenuation 1ntroduced by thirty uints of such a line. Tl'llS will depend on the resistance of the wire employed. If the coils have each a resistance of R=9 ohms, we have by (3) a=%/% whence (8) a.=9/520, which substituted. in the equation for 1,, in terms of I gives the line.

(9.) I =.6XI where I is the current in the 30th section of These results show the method of obtain- 'ing proper constants for the required retardation per section of the line and show. also, incidentally, how much the current will be reduced in intensity. by the action of the line. The example is only illustrative and it is easy to obtain much less resistance in the coils than the 9 ohms given in the example, and

therefore possible to obtain less attenuation than that specified, while preserving the proper retardation per section of the line.

There is one other consideration in the del S1011 of the retardation line; namely, it is occur in in iportantto have the retardation substantially independent of the frequencies that the source of sound, so that the of a multiple sound which arrives at the car will not be modified in quality by the operation of the line. This result is attained most perfectly by making the time retardation per section of the line small, so that the retardation time per section of the line, smaller than that here specified, may be employed. On the other hand if the retardation per section is made too small, the number of in a practical case may become too large for easy construction. The value of the time retardation per section chosen in the example is sufficiently large to permit of an economical construction and is sufliciently small to have "the line transmit'all frequencies less than about four thousand cycles per second, and therefore permits transmission of sounds of significant audible frequencies.

Fig. 5 shows a wiring diagram of an electric compensator for use with two rows of microphones, twelve microphones in each row, and Fi 6 shows the assembly of the several switc es are indicated diagrammatically in Fig. 5.

Referring to Fig. 5, reference numerals 201 to 212 indicate terminals which are connected to twelve microphones placed in a row, for example, on the port side of a ships hull, and reference numerals 301 to 312 indicate terminals which are connected to a similar row of twelve microphones, placed for example on the starboard side of a ships hull. -All of these microphones have their other terminals connected in parallel to a common connection, as shown, which is connected at the binding post 213 of one side of the battery 214. The other side of the battery 214 is connected through a switch 215 to a common lead 216 from'which electric currents pass through the primar coils P of twenty-four transformers num cred 217 to 228 and 317 to 328 inclusive. The secondaries of these transformers are marked S, of which there are two classes to be referred to, as

formers 217 and 228 and of the port transformers 317 to 328 res ectively. By means.

oint dou le throw swltch, th blades of whic are indicated at B, either the starboard secondaries or the port secondaries can be connected to the input terminals of the compensator which are formed by the leads 401 to 412 inclusive. The other sides of the transformer secondaries are connected to a common lead 413.

When the switch blades B are all thrown to the right in Fig. 5, the-secondary of the transformer 217 is connected to one end of a retradation line 501 of seven sections. The secondary of the transformer 219 is connected to the other end of this retardation line. At the several sections of this retardation line are switch contact blocks numbered 511 over which a brush 521, is movable. This brush is sections required and their connections which Y the several rings 531, 532, 533 and 534 may.

V are in general still out of phase, an

carried on a ring 531. The electric currents from the secondaries of the transformers 217 and 219 pass into the two ends of the retardation line 501 and out through the brush 521 to the ring 531.- Current from a secondary of the intermediate transformer 218 passes through the fixed retardation line of three elements 502, directly to the ring 531. By this process currents from the secondaries of the first three transformers 217, 218 and 219 of the series are led to the common point 531. By moving the brush 521 the time retardation of the current from the transformer 217 may be made less than that from the transformer 218, while retardation of the current from the transformer 219 is made greater than that from218 by an equal amount; so that if the secondaries of the transformers 217, 218, 219 are actuated by three microphones equally spaced, currents which are out of phase in the microphones may be brought into phase at the ring 531'. In a similar manner the currents in the secondaries of the transformers 220, 221 and 222 are brought together at the ring 532, in phase with each other, but not necessarily in phase with the current at 531. In like manner the rings 533 and 534 collect currents from the remaining two groups of three microphones each. The condensers 541, which are connected to the inductances 542,015 the eight retardation lines 501 to 508 inclusive have their opposite terminals connected in multiple to the common return lead 413.

It is now necessary to have the manipulation of such a character that the currents in be further united. This is partially done by means of two retardation lines 601 and 602 each of which consists of inductances 642 in series and capacities 641 in shunt. The currents from the rings 531 and 532 pass to brushes 551 and 552 respectively which are connected by the leads 661 and 662 respectively to the two ends of the retardation line 601. The several sections of this retardation line have contact blocks 611 (not shown in Fig. 5) over which pass-a brush 621 connected to the ring 631. By a pro er adjustment of the brush 621 along the locks'61l, .the currents which in general were out of phase in the ring; 531 and. 532 are brought into phase at th' ring 631. In like manner the currents from the rings 533 and 534 pass throu h the retardation line 602 and are 'brou t, into phase at the ring 632. The rings 631 and 632 are connected by brushes 651 and 652 to leads 761 and 762 respectively .Which are connected with two'L-sha 711 and 712 of the series of .mova le' blocks of the retardation line 701. The currents entering these blocks 711 and 712 res tively must be still further retarded with reference one to and this-is done in the retardation the other,

'used to combine the .ment witho'ut'the closed in the circuit 811. This connects the two telephone receivers in multiple to the edblock if the contact line 701 of inductances 742 in series and capacities 741 in shunt. This line consists of twenty three sections. with each section connected with the up er and lower brushes 721 and 722 respectively of two adjacent pairs of brushes. as shown in the diagram. The connections are so made that the rectangular blocks 7130f the seires of movable blocks bridge the brushes of each pair in such a manner that the inductance coils 742 of the sections are connected in series respectively on each side of the two L-shaped blocks 711 and 712. The blocks 711 and 712 interrupt the series connection so that the currents flowing into these blocks pass independently one from the block 711 tothe left along the retardation line and out through the lead 801 to the telephone'receiver 803; while the current entering the block 712 passes out to the right along the retardation line and through the lead 802 to the telephone receiver 804. These currents which pass through the two telephone receivers then unite in the common lead 805 communicating with the lead 413, and thence to the common junction of all the secondaries of'the transformers 217 and 228 inclusive. By the proper adjustment of the movable ceiver so as to bring these currents into phase,

and to effect a proper bin'aural centering.

The currents from the six transformers 217 i to 222 have been brought into phase at the ring 631 by the retar ation lines 501, 503, 504, and 601 so thatthe sound in the left hand telephone receiver is the currents from the six transformers 223 to '228 have been brought into phase at the ring 632.

The function of the line 701 with the connections-from its two ends to the telephone receivers separately is to bring the two maximum sounds in the two receivers into phase so as to cause the physiological sense of the binaural centering of the sound.

The retardation line 701- may however be, currents so-as to produce a maximum sound in each telephone receiver but withoutthe bin'auralsensation. To use the compensator as a pure maximum instrubinaural, the switch 810 is common junction point of the leads 801 and 802 from the two ends of the line 7 01. The

get 'no binaural sensation but )locks of the line 701 are pro AT listener will erly positioned to bring the currents from t e rings 631 and 632 into phase with each other, the listener will get a maximum sound in the telephone receivers.

It is to be noted that the same position of the contact blocks of the line 701 which gives v a'maximum independently of the retardation line 701. Similarly ting,

binaural centering when the switch 810 is open, gives a maximum when this switch is closed. The binaural and the maximum may therefore be used to check each other, by simply closing and opening the switch 810.

While the binaural setting of the compensator is usually employed in determining the direction of submarine sounds such as that of a ships propeller, the setting by means of the maximum may be employed where the sound is of such a character that binaural centering is diflicult, as forexam le on a sound source emitting a purr soun or sustained musical note.

If the compensator is designed to be a maximum instrument with no binaural Setthe final retardation line 701 can be made much simpler than that shown in the drawing because the retardation line 701 as shown is designed particularly for binaural direction determination. If a maximum alone is to be had, the line 701 may be replaced by a line of the type shown at 601, 602 and the leads 761, 7 62 connected to the ends of such a simple line and a simple brush connected with a single receiver would be arranged to make contact at the points between the sections of the line, substantially. in the same manner as the brush 621 makes contact with the contact blocks of the line 601.

In Figure 6 is illustrated diagrammaticallythe arrangement ofthe several switches for the retardation lines. The switches are operated from a common shaft 900, which is shown broken for purposes of illustration.

Corresponding parts on-Figs. 5 and 6 are indicated by the same reference numerals. The fixed retardation lines 502, 504, 506, and 508, are indicated at the bottom of Figure 6. The variable retardation lines 501, 503, 505 and 507 are shown as surrounding the lower four switch plates. The small arrow heads 905 on the leads indicate that they are continued around behind the switch plates. The brushes 521, 522, 523,

rotatable rings 531, 532, 533, 534 respectively and move over the contact blocks 511, 512, 513, 514 respectively. The brushes 551, 552, 553, 554 are connected throu h the leads 661, 662, 663, 664 respectively tot e opposite ends of the respective retardation lines 601 and 602. The common return lead is indicated at 413 corresponding to the same numbered lead on Figure 5.

The construction of the/switches for the two retardation lines 601 and 602 is similar to the four lower switches, except that there are eleven instead of seven contact blocks.

The switch for the line preferably used with 701 is shown at structure of this switch is the same as the switch shown in Figures 3 and 4. The series of contact blocks 711, 712 and 713 are carried on the underside of a rotatable disc 7 7 0.' The slip ring-7 82 and 783 are also carried on the 524 are carried by the and the the top. a The general and 762 are connected to the slip rings 782 and 783. Except that these slip rings and brushes are not shown in Figure 5, the connections in Figure 5 are the same as in Figure 6.

The general arrangement of parts of this switch is the same as that shown in Figure 3 and Figure 4, exceptthat the electric currents are lead into the retardation line through the L-shapedswitch blocks and the telephones are connected to the ends of the line, whereas I in the switch shown in Figures 3 and 4, the currents are led into the ends of the line and the telephone receivers are connected to the L-shaped blocks. These two methods of connection are equivalent.

The disc 770 is provided with a scale, not

shown, similar to the disc 85, in Figure 4. This scale is calibrated in angles so that when the observer makes a setting either by means of the binaural or the maximum, he can read directly the angle of incidence of the sound with respect to the base line of the row of microphones.

The shaft 900 connects the switches fOr-the several retardation lines together so that the blocks and brushes for the several lines move in unison and in proper angular relation to each other.

Let the eight retardation lines 501, 502, 503, 504, 505,506,507 and 508 connected to the secondaries ofthe transformers be designed as lines of class I. Let the two retardation lines 601 and 603, be called lines of class II. Let the retardation-line 701, be called a line of of each section of the lines. of

class I. Let L and C, be the inductance and capacity of each section of the lines of class class III. Let L and C, be the inductance and capacity tion points of the lines ofthe several classes,

riiiefi'tiaiin relations must be approximately fule v The current is fed to one end of the retardation line 601 through the lead 661, through three retardation branch lines, one branch being through the fixed retardation line 522 other branches being the two parts of the retardation line 501, at the two sides of the contact point 521, respectively. Similarly the other ends of the retardation lines .601 and 602, which are of class II, are each fed by three retardation branch lines of class I. To minimize reflection the relation between the inductance and capacity of the lines shouldbez n= la .(10).

tn, E (11-) 0.

These equations are the conditions requisite for a maximum transmission of current to a line where the currents in the tributary branches are in phase with each other. For a maximum input of current to each of the lines of class I and to minimize electrical reflections at the input terminals of these lines,

the following relation should also be approximately fulfilled.

L3,. (1'3) where Z =impedance of the translating device fed by a single branch of the line of class-III, (in the present case one of the telephone receivers). i

In addition to these relations let the time retardation persecond of the lines of classes I. II and III be respectivel t t t By combining the several equations we obtain When t t t and Z, are given,

C can be calculated.

L L L and C C 1 2 For example let t, t i 6.5 X 10 seconds and let Z 195 ohms, then (17) L =.0127 henry L,.=.O042 henry L .0021 henry (18) C,= X 10- farads C 1 X 10 farads C 2 X 10- farads Similarly the impedance of the translating device to avoid reflection can be'calculated. In the case given above each of the telephone receivers should have an impedance Z given by the equation.

1. A combination with an electric line formed in a plurality of sections, of a switch comprising two rows of brushes arranged in opposing pairs, and connections from each brush of a pair to the ends of two adjacent sections of the line, and a plurality of blocks disposed in a row and relatively movable along the rows of brushes, two adjacent blocks being shaped, one to extend across two adjacent brushes of one row and the other across two adjacent brushes of the other row so that each block is always in contact with a brush of the respective rows, these two blocks being spaced so as to leave an inter ruption in the line between, and blocks arranged in a series at each side of these two blocks for bridgin across opposing brushes and maintaining tie sections of the line in series at either side of the first two blocks, substantially as described.

2. An electric compensator comprising a series of retardation branch lines and a retardation line common to all of said branch lines and connected thereto, each of said lines comprising inductances in series and capacities 1n shunt and arranged in sections, the ratioof the inductance to the capacity. per section of each of the branch lines being n times the corresponding'ratio for the sections of the retardation l1ne common to said branch lines as described.

3. An electric compensator adapted for use with receivers of wave' energy in which electric currents are each. ear, means for transmitting the currents from a plurality of receivers one translating device including electric reproduced, comprising two auditory translating" devices, one for tardation lines for bringing the currents into phase and causing a sound maxlmum and for transmitting the currents from others of the receivers to the other translating deviceincluding electric retardation lines for bringing the currents into phase and causing a sound maximum, and a retardation line for bringing the currents in the two translating devices into phase with each, other for a binaural setting, substantially as described.

4. A compensator adapted for use with a plurality of electric receivers of wave energy comprising two auditory translating devices, one for each ear, and means for transmitting the wave energy from the receivers to the auditory devices, including electric retardation lines for producing a maximum combined with a binaural at the translating devices, substantially as described.

5. A system for the reception of wave energy comprising a plurality of groups of receivers, each group being made up of at least two receiver units spaced in a definite configuration, means associated with said receivers for translating said wave energy into electric currents, means comprising tributary retardation lines associated with said translating means for making the currents in the group additive in phase, an indicating means, and means for associating the group currents, including a main retardation line for bringing said group currents in phase at said indicating means and means for varying the amount of retardation of said retardation lines.

6. A system for the reception of sound energy comprising a plurality of groups of sound receivers, each group being made up of at least two sound receiver units spaced in a definite configuration, means associated with said sound receivers for translating said sound energy into electric currents, means comprising tributary retardation lines associated with said translating means for making the currents in the group additive in phase, an indicating means, and means for associating the group currents, including a main retardation line for bringing said group currents in phase at said indicating means and means for varying the amount of retardation of said retardation lines.

7. A system for determining the direction of a source of sound energy comprising a plurality of groups of sound receivers, each group being made up of at least two sound receiver units spaced in a definite configuration, means associated with said sound receivers for translating said sound energy into electric currents, means comprising tributary retardation lines associated with said translating means for making the currents in the group additive in phase, an indicating means, and means for associating the group currents, including a main retardation line for bringing said group currents in phase at said indicating means and means for varying the amount of retardation of said retardation 1ines,.and means indicating, at the time said currents are in phase, the direction of the sound source.

GEORGE w. PIERCE. 

